1. Field of the Invention
The present invention relates to a warming-up system for warming up an engine for an automotive vehicle.
2. Description of the Related Art
Japanese Patent Laid-open Publication (kokai) No. 62-67,244 discloses technology capable of adjusting the number of engine rotation in a region where the engine is unloaded and the number of engine rotation is low, by providing an intake system with a bypass for bypassing a throttle valve and providing the bypass with a bypass valve for adjusting the amount of intake air.
Japanese Patent Laid-open Publication (kokai) No. 2-115,537 discloses means for changing an overlap period of time during which the intake valve and the exhaust valve are both open.
Further, Japanese Patent Laid-open Publication (kokai) No. 1-159,431 discloses an exhaust valve timing variable mechanism for changing a valve timing of the exhaust valves. The exhaust valve timing variable mechanism is adapted to change a timing for opening the exhaust valves so as to open the exhaust valves at a retarded timing during the cold time, as compared with during the warm time.
It should be noted herein that the shortening of the time required for warming up the engine is effective for measures to compete with engine emissions because the burning state within the engine is unstable and hazardous ingredients are prone to increase in exhaust gases when the engine is in a cold state.